This invention relates to flexible filament cutting devices in general and, more particularly, to an improved device for metering the length of a flexible filament cutting element in such devices. Flexible filament cutting devices generally include one or more flexible filament cutting elements coiled about a spool which is rotated at a high rate of speed to impact cut vegetation for edging and trimming application.
As a result of normal usage, flexible cutting elements often become frayed or broken, thus shortening their effective cutting lengths. Therefore, it is necessary to provide apparatus for uncoiling, playing out, or otherwise providing a new length of flexible cutting element to replace the lengths which become unusable under normal operating conditions. Typically, the rotation of the spool is imparted by a high speed, low torque electric motor. Excessive flexible cutting element length increases the probability of electric motor burn-out. Thus, it is desirable to provide an apparatus which limits the play-out of the flexible cutting element to predetermine discrete increments and furthermore maintains the flexible cutting element length less than a predetermined maximum.
Devices are known in the prior art for metering the length of the flexible cutting element. In one such device, a flexible cutting line is wound about a spool. The spool has a square recess and is spring biased into a position where it engages a square-headed bolt secured to the motor shaft. When it is necessary to uncoil additional cutting line, the device is de-energized and allowed to stop rotating. Then, the spool is manually depressed against the biasing force of the spring to disengage the bolt and recess. The spool is then free to turn. Upon release, it may again engage the bolt head. The operator rotates the spool until he judges that the necessary additional length of flexible line has been removed from the coil.
This device has a number of shortcomings. First, the device must be de-energized and allowed to stop rotating prior to line metering. Second, the line must be manually pulled out from the spool to increase effective cutting line length. Third, the amount of line added is controlled primarily by the operator's estimate as to the needed additional length. Fourth, the maximum length of the cutting line is limited only by the amount of line pulled out by the operator. If, therefore, excess flexible cutting line is uncoiled, the probability of electric motor burn-out increases substantially.
The present invention eliminates the disadvantages inherent in the prior art devices in that it provides a positive escapement means which limits the play-out of the flexible cutting element to discrete predetermined increments. Additionally, a cutting blade is provided to sever excessive flexible cutting element when the length exceeds a predetermined maximum value. Finally, the present invention automatically meters flexible cutting element while the device is operating as opposed to requiring that the device be de-energized prior to metering the additional flexible cutting element.